EMPLOYEE BENEFIT PLANS (Tables)

6 Months Ended

Jun. 30, 2018

Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]

Components of the Net Periodic Benefit Cost

Components of the net periodic benefit cost of PLC's defined benefit pension plan for the three and six months ended June 30, 2018 and 2017, are as follows: 

	For The Three Months Ended June 30,										For The Six Months Ended June 30,
	2018					2017					2018					2017
	Qualified Pension Plan			Nonqualified Excess Pension Plan		Qualified Pension Plan			Nonqualified Excess Pension Plan		Qualified Pension Plan			Nonqualified Excess Pension Plan		Qualified Pension Plan			Nonqualified Excess Pension Plan
	(Dollars In Thousands)
Service cost — benefits earned during the period	$	3,441		$	387	$	3,348		$	334	$	6,882		$	774	$	6,696		$	668
Interest cost on projected benefit obligation	2,397			359		2,191			297		4,794			718		4,382			594
Expected return on plan assets	(4,026		)	—		(3,352		)	—		(8,052		)	—		(6,704		)	—
Amortization of prior service cost	—			—		—			—		—			—		—			—
Amortization of actuarial loss/(gain)	—			265		—			118		—			530		—			236
Preliminary net periodic benefit cost	1,812			1,011		2,187			749		3,624			2,022		4,374			1,498
Settlement/curtailment expense	—			—		—			—		—			—		—			—
Total net periodic benefit costs	$	1,812		$	1,011	$	2,187		$	749	$	3,624		$	2,022	$	4,374		$	1,498